Reducing resistant weeds

Weeds are a chronic crop pest, resulting in $33 billion in lost production plus another $5 billion in herbicide costs in the U.S. The most widely used herbicide in Minnesota, glyphosate, no longer works as effectively on problematic weeds such as giant ragweed. In 2014, 1.5 million acres of corn and soybean in Minnesota were considered "heavily infested" with herbicide-resistant giant ragweed.

Jeff Gunsolus, Extension weed scientist, found that weed emergence was reduced when wheat or alfalfa were planted in rotation with the corn or soybean crop. When combined with other practices to prevent new weed seeds from entering the soil, long-term giant ragweed management can be accomplished. Extension educators contributed to the project, which was co-led by graduate student Jared Goplen.